Industrial action at Irish Rail could mean strikes or a work-to-rule, unions have warned their members.

And Dublin Bus drivers are considering a range of options, including a no-fares day, an all-out strike and 24- or 48-hour work stoppages in pursuit of a pay rise higher than 8pc over three years, according to the general secretary of the National Bus and Railworkers Union (NBRU), Dermot O'Leary.

In a notice to Irish Rail drivers as they begin balloting for industrial action, Siptu blames the company's refusal to discuss issues, including a shorter working week, for the breakdown of talks.

Discussions on issues, including driver training, mentoring, productivity and a shorter working week, collapsed at the Workplace Relations Commission last Thursday.

The union instructs members that the work-to-rule may include an overtime ban, non- co-operation on roster changes and a refusal to carry out senior roles or work in depots other than their own. They will not do any new work and will refuse to swap rest days.

The notice was posted as the row between unions and Irish Rail deepened after the company accused Dart drivers of engaging in unofficial industrial action by blocking the training of nine drivers.

An Irish Rail spokesman said training, including in-cab familiarisation, was a requirement of all drivers but unofficial action orchestrated by unions meant there was a collective refusal to participate in mentoring.

Meanwhile, Siptu has confirmed that it will ballot its members at Dublin Bus next week after they rejected a Labour Court proposal for an 8pc pay rise over three years.

The NBRU is due to ballot its members tomorrow and Friday.

However, both unions have emphasised that they are available to re-enter talks.

Mr O'Leary said that his members were almost certain to back industrial action to send a clear message to Dublin Bus that they deserve a pay rise at least in line with the norm set by the Labour Court in the Luas dispute.